How to secure access to Mongo DB Atlas

I want to use Mongo Atlas as my DB on my application, but I am facing an issue:

I am using a Cloudflare Proxy. So anytime there is a new request to my website, the IP changes. So, how can I secure the access to my DB without having a unique IP address to access from?

I’ve tried to add to the whitelist all the Cloudflare IPs, but Mongo does not accept IpV6 ranges. Is there any way to restrict the access by domain? Any other solution to have secure connection to MongoDB in my case?

Note that Atlas maintains a posture of security in depth, requiring database authentication and TLS network encryption on top of the firewall: so you may consider opening up a wider public IP block